One thing I have learned to help me to relax before shooting is to stay focused on the process and not the outcome. I'm not worried about going fast or winning I just want to perform the fundamentals correctly. Working through my mental routine helps keep me that way. I already know how I'm going to shoot the stage and maintaining visual patience isn't really something that makes my heart race. Now I'll admit that my hand often shakes a little after a stage but going into the next one I'm back to my routine and process focus.